I don't know if 'items' is the right attribute to check, or if it would actually be better to change to isinstance(data, dict). What other data structures are mean to be acceptable? What is "something similar" to a dict?

For whoever wants to work on it, regarding
...
I don't know if 'items' is the right attribute to check, or if it would actually be better to change to isinstance(data, dict). What other data structures are mean to be acceptable? What is "something similar" to a dict?

There is some custom "Mapping types" in sage like FreeModuleElement_generic_sparse, which implements items and iteritems but doesn't inherit from dict.

Is there a followup ticket to modify src/ext/doctest/python3-known-passing.txt? Should that happen for every beta, or just every actual release? Anyway, we should add algebras, data_structures, homology, modular, modules, schemes/curves, schemes/product_projective. What am I missing?

Regarding matroids: there is some piece of underlying data which is intrinsically unordered, and it is causing all sorts of failures. I don't know if it's best to mark them all # py3 random or to sort the data so this doesn't happen. Is there an active Sage developer who knows enough about matroids to help make this decision?

#27773 and #27774 fix various issues in Python 3 with src/sage/numerical/backends/cplex_backend.pyx and 1 in gurobi_backend.pyx. Cplex <= 12.8 is needed to test these tickets. Cplex >= 12.9 cannot be used yet (see #27790).

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).